| ABX3 type of perovskite solar cells are moving forward in the direction of commercial applications,mainly because of its simple preparation process and low cost.However,due to the low electron migration rate of commonly used electronic transmission(PC61BM)materials,the polycrystalline properties and instability of perovskite,it still face many challenges on the road of industrialization.Therefore,how to improve the electronic transmission layer material,obtain high quality perovskite film and improve device stability,has become an important prerequisite to solve the practical application of perovskite solar cells.In order to solve the above problems,the author applied imidazolidine functional materials to the electron transport layer and perovskite active layer by means of doping and interfacial modification,and relies on the strong electron absorption effect of the imidazole-group to improve the charge transfer rate of the electron transport layer and reduce the defective density of the perovskite.In this paper,16.88%photoelectronic conversion efficiency is achieved in solar cells with CH3NH3PbI3 material as the photoactive layer,and 14.1%photoelectronic conversion efficiency is achieved in CsPbI2Br perovskite devices,and the stability of the device in air is significantly improved.Specifically,the research content of this paper is as follows:1.Study on electronic transport materials doped with amphoteric imidazole or benzimidazole:First of all,imidazole and benzimidazole are doped into the electronic transmission layer(PC61BM)and perovskite solar cells are prepared with ITO/PTAA/MAPbI3-xCl3/PC61BM/BCP/Ag.The results show that p-hotoelectronic conversion efficiency of undoped PC61BM devices is only 14.38%,while the efficiency of devices is increased to 15.62%and 16.74%,respectively.Further analysis shows that the two doping agents can make the PC61BM film more flat,and the electron migration rate has been greatly improved,both of which have played a role in promoting the transfer of photo-carriers from the perovskitelayer to the cathode.In addition,due to the fact that imidazole and benzimidazole have both Lewis acid and Lewis base,the doped PC61BM which be used on the surface of the perovskite can also play the purpose of passivated perovskite surface defects,thus improving the photoelectric conversion efficiency of the device.Meanwhile,doping PC61BM can also improve the stability of the device,the main reason for the increase in device stability is that the imizadole-group can interact with iodine ions which can reaction with Ag,limiting the spread of iodine ions to Ag electrodes,thereby slowing down the degradation of perovskite.2.Regulation of perovskite crystal and defect passivation by imidazole doping:In order to improve the quality of perovskite film,imidazole is used as a doping agent for the photoactive layer of perovskite.The perovskite solar cells structure with ITO/PTAA/MAPbI3/PC61BM/BCP/Ag,the photoelectronic conversion efficiency of the device was significantly improved by the use of imidazole additives,and its efficiency increased significantly from 14.65%to 16.88%,of which the filling factor and open circuit voltage were significantly improved.Studies have shown that imidazole additive can not only regulate the crystal growth of perovskite and enlarge the grain size,but also act as Lewis acid and passivate the defects in perovskite.In addition,due to the improvement of the crystal quality of perovskite,the passivation effect of imidazole on perovskite can protect the crystal boundary from water vapor or heat induced ion migration,which in turn improves cells stability.3.Study on 3D/2D perovskite(CsPbI2Br)cell structure induced by benzimidazole iodide salt:In view of the excellent thermal stability of all-inorganic perovskite compared with organic inorganic hybrid perovskite materials,and the fact that all-inorganic perovskite materials are prone to phase transition,we studied the application of imidazolidine salt in inorganic perovskite cells in the following work.We synthesizes two kinds of imidazole derivatives,which are applied to the surface of CsPbI2Br,and confirms that benzimidazole iodide can form a 2D structure of perovskite on the surface of CsPbI2Br,thus constructing a layer of 3D/2D mixed structure.The preparation of the structure of ITO/NiOx/CsPbl2Br/PC6iBM/BCP/Ag perovskite solar cells,compared to the undecorated reference devices,using 3D/2D structure can make the efficiency increased from 10.3%to 13.9%.Further studies show that the defect state density at the 3D/2D interface is effectively reduced,thus reducing the non-radiation composite of the carrier at the interface and increasing the open voltage of the device(1.059 V to 1.162 V).Because of the excellent stability of 2D structure perovskite,the stability of 3D/2D structure devices has been significantly improved. |
